Residents were informed this past summer that the risk of explosion at the site, used to store ammunition during the Second World War, was higher than expected.

(KEYSTONE / ANTHONY ANEX)

The Swiss government announced Wednesday that it will reinforce monitoring of the former Mitholz ammunition stockpile in the Bernese Oberland. Authorities hope to reduce or eliminate the risk of explosion by mid-2020.

External sensors are currently being installed, and video and thermal cameras will also be made available on the site. At the beginning of next year, a system will also be installed to measure escaping gas.

While increased monitoring is necessary, immediate action to protect the local population is not needed. Residents must, however, prepare a cellar where they could spend at least a day in case of emergency, authorities said in a statement on Wednesday.

In July this year, local residents were shocked to learn that the site, which was used to store some 7,000 tonnes of raw ammunition during the Second World War, could still present a danger to the public. Some 3,500 tonnes of ammunition are still believed to lie dormant.

The Mitholz site was the scene of a tragedy in 1947, when the depot, which consisted of six rooms under a mountain connected by a railway tunnel, exploded and killed nine people.

According to a risk assessment by the defence ministry, rockfalls, collapse, and self-ignition of explosives are an ongoing risk and could cause further damage.